(a) Field of the Invention
The present invention relates to a hydro forming apparatus for making U-shaped products. More particularly, the present invention relates to a hydro forming apparatus for making U-shaped products, which can adjust a shape of bent tube thereby improving product quality.
(b) Background
Referring to FIG. 10, a process for making U-shaped products will be described in detail.
As shown in FIG. 10, after a tube is bent into a U-shaped tube, the U-shaped tube is free formed into a rough U-shaped product. After that, a hydro forming process is performed by applying hydraulic pressure to the free formed U-shaped tube and a U-shape product is made by cutting ends of the tube.
In a case that a tube is bent into a U-shaped tube, the bent tube tends to restore its original shape to some degree, instead of maintaining its bent shape. This phenomenon is called spring back. For this reason, the bent tube should be further bent so as to complete a bending process. If a bent tube that does not undergo such adjusting process is inserted in a hydro forming apparatus, as shown in FIG. 11, pinching may occur and production quality may be deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.